1-bit and 2-bit Characters

We have two special characters:

• The first character can be represented by one bit 0.
• The second character can be represented by two bits (10 or 11).

Given a binary array bits that ends with 0, return true if the last character must be a one-bit character.

Example 1:

Input: bits = [1,0,0]
Output: true
Explanation: The only way to decode it is two-bit character and one-bit character.
So the last character is one-bit character.

Example 2:

Input: bits = [1,1,1,0]
Output: false
Explanation: The only way to decode it is two-bit character and two-bit character.
So the last character is not one-bit character.

Constraints:

• 1 <= bits.length <= 1000
• bits[i] is either 0 or 1.

SOLUTION:

class Solution:
    def isValid(self, bits, i):
        if i == 0:
            if bits[0] == 0:
                return True
            else:
                return False
        if i == 1:
            if bits[0] == 1:
                return True
            elif bits[1] == 0:
                return True
            else:
                return False
        if bits[i - 1] == 1 and self.isValid(bits, i - 2):
            return True
        if bits[i] == 0 and self.isValid(bits, i - 1):
            return True
        return False

    def isOneBitCharacter(self, bits: List[int]) -> bool:
        if len(bits) >= 2:
            return self.isValid(bits, len(bits) - 2)
        else:
            return True